This proposal requests funds for the purchase of a plasma desorption mass spectrometer (PDMS) with time-of-flight (TOF) analytical capability. It is planned that the instrument will serve primarily 12 user groups in 10 departments at the University of Washington. Virtually al of the projects are directed at analysis of peptides of biomedical interest. This instrumentation will provide these users with access for the first time to mass spectrometer analyses of peptides of mass greater than 3000 amu. This biomedical community will benefit from access to this rapid, sensitive, flexible technique for examining peptides of high mass, for detecting posttranslational modifications, and for application of chemical strategies of partial structural analysis of proteins.